In recent years, as interest in global warming and power saving increased, a variety of measures are proposed in a variety of fields. For example, in a field of office automation (OA) devices used in offices or homes, a variety of techniques have been developed in view of power saving.
In an image forming apparatus which includes a variety of functions such as a copy function, a scan function and a print function, a power saving mode such as a standby mode and a sleep mode is set in addition to a normal operation mode, to achieve power saving. In the normal operation mode of the image forming apparatus, for example, when reading an original document for printing, it is necessary that an electrostatic latent image on a photosensitive drum should be able to be rapidly transferred onto a recording paper, so as to complete printing without standby. Thus, a heater for heating and fixing toner should constantly maintain a heating state.
In a print mode, it is necessary to supply electric power in order to maintain a variety of operations such as electrical connection to a light source driving motor, a driving motor for transporting recording paper or the like, and the fixing heater. In the image forming apparatus including the variety of functions, the print mode is an operation mode in which load to a power source becomes the maximum.
The standby mode refers to an operation mode in which the image forming apparatus is in a standby state to be able to perform printing anytime. An operation of an electronic circuit approximately corresponds to the print mode, but in reality, the printing should not necessarily be performed. Thus, it is not necessary to operate the variety of motors or the heater. For this reason, in the standby mode, the motor driving may be turned off, or the electrical connection to the heater may be cut off, to significantly reduce the load to the power source compared with the print mode. When a print instruction is input from a control panel, an external personal computer or the like in the standby mode, the standby mode immediately shifts to the print mode to perform printing.
The sleep mode refers to an operation mode which is automatically transited from the standby mode when the standby mode is continued for a predetermined time, wherein the load to the power source becomes the minimum. Specifically, except power supply to the function of communicating with the control panel, the external personal computer or the like, power supply to sections which perform the other functions is entirely stopped. If the print instruction is input from the control panel or the external personal computer, a print instruction signal is recognized by a communicating section which is supplied with electric power. Then, the communicating section gives an instruction to supply electric power to a necessary electronic circuit, so that the operation mode returns to the standby mode and then shifts to the print mode.